A cryptanalyst tries to break some cipher text communication. The only clue he has is that the transferred text are XML files. Does this clue provide any helpful information for the cryptanalyst? If so, what would be his next step in his analysis?

Sample XML file for your reference:

Daren

Aron

Reminder

Let's meet this weekend!

You might have seen that many cryptographic algorithms make use of XOR function. Why is this function used in cryptographic functions?

A real-time sensor continuously generates data that must be encrypted and transmitted to a remote server. Which cipher do you think is best applicable here and why? Write 2 ways to secure your stated cipher and harden the cryptanalysis.

Which mode of operation of block ciphers is suitable and efficient to run on computers with multiple processors? Explain why your stated mode is suitable.

 

Alice and Bob, each generate a pair of keys. (PuB, PrB) is the public key, private key pair of Bob. (PuA, PrA) is the public key, private key pair of Alice. They share their public keys. Bob wants to send the following message to Alice. 

Dear Alice, Our client meeting on coming Monday is confirmed, Regards, Bob

Now Bob wants to digitally sign his message, then encrypt the complete signed message and send to Alice. Write the steps involved in digitally signing, encrypting and sending the message. Also mention what are the attacks the transmission is protected from.

SHA-512 appears to provide unassailable (invulnerable to attack) security compared to its previous versions. What makes it more secure?

Why can't a hash function be used directly for message authentication? Name the algorithm that is designed to solve this issue? What is the use of nonce and associated data in a message authentication algorithm?

What is the reason for introducing the Optimal Asymmetric Encryption Padding (OAEP) procedure in RSA encryption? What purpose does this procedure serve? What is the difference between a Mask Generation Function and a Hash Function?

We know that Diffie-Hellman key exchange algorithm is vulnerable to man-in-the-middle-attack. What makes it vulnerable to such an attack? Is there an approach to protect the algorithm from such an attack? Explain.